albertogpz commented on a change in pull request #6663:
URL: https://github.com/apache/geode/pull/6663#discussion_r681977195
##########
File path:
geode-core/src/main/java/org/apache/geode/internal/cache/wan/parallel/ParallelGatewaySenderQueue.java
##########
@@ -1404,13 +1404,19 @@ void
peekEventsFromIncompleteTransactions(List<GatewaySenderEventImpl> batch,
}
}
if (incompleteTransactionIdsInBatch.size() == 0 ||
- retries++ == GET_TRANSACTION_EVENTS_FROM_QUEUE_RETRIES) {
+ retries >= sender.getRetriesToGetTransactionEventsFromQueue()) {
break;
}
+ retries++;
Review comment:
@agingade I have given a bit of thought about using wait and notify
instead of sleep but I have come to the conclusion that it is not a good idea
in this case.
According to your suggestion, instead of `sleep(time)` we could call
`wait(timeout)` and then `notify()` whenever an event is added to the queue.
This way, every event added to the queue will awake the thread that must look
for events in the queue to complete transactions inside a batch.
The problem is that the event added to the queue that will provoke the
awakening of the waiting thread may not be the one required to complete the
transaction so the thread could have been awaken in vain.
If a lot of events are entering in the queue at a high rate, it might be
that, a lot of awakes will be required before the events to complete the
transaction enter the queue. This would require to increase the value of the
retries. But this is dangerous as the WAN replication rate could greatly
decrease.
The original implementation of this feature did not contemplate any sleeps.
It just retried several times the search in the queue to retrieve events to
complete transactions when they were not found, assuming that the events for a
transaction should arrive to the queue very close in time. I observed that
sometimes the retries were done so quickly that even if the number of retries
was high, still some batches had to be sent with incomplete transactions and
that is why I changed the behavior in this PR to wait a little before retrying
by means of sleep.
If you do not agree with my conclusions, I am open to discuss them with you
by e-mail, chat or videoconference.
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